The document proposes a methodological approach to modeling software-intensive systems. It defines a "block" as a unified concept for systems and elements at any level, with properties of purpose, elements, interaction, and organization. It describes modeling the system across four views - environment, services, structure, and behavior - and at different phases of a systems engineering process, including requirements analysis, functional analysis, and design synthesis. The approach aims to provide consistency within and between models of the system at different levels.

1. Software Intensive Systems Modeling
A Methodological Approach for MBD
Dr. Amir Tomer, PMP, CSEP, CSQE
Head, Software Engineering Department
Kinneret Academic College on the Sea of Galilee, Jordan Valley, Israel
amir@amirtomer.com
Dr. Amir Tomer, Kinneret College 1 Software Intensive Systems Modeling

2. Motivation
• The quality of a product depends much on the quality of its requirement and
design specifications
– Missing, vague or sloppy specifications lead to wrong implementation, inaccurate
testing and poor product usability
• Modeling techniques and languages are increasingly used for software
engineering, replacing textual specifications with visual ones
• However…
• In many software-intensive systems, modeling is not applied properly,
according to
– Lack of modeling methodology
– Complexity of languages and tools
– Inconsistencies between development levels
• Particularly between the system and the software level
Dr. Amir Tomer, Kinneret College Software Intensive Systems Modeling2

3. Our Approach
• We propose a methodological approach to software-intensive
system modeling, which provides
– Systematic modeling for all system breakdown levels
– Consistency within and between system and software level models
– Simple and “just enough” application of modeling elements
(UML/SysML)
Dr. Amir Tomer, Kinneret College Software Intensive Systems Modeling3

4. “System” – a recursive-hierarchical Structure*
*ISO/IEC/IEEE 15288
system
element
system
element
system
element
system
system
element
system
element
system
element
system
element
system
element
systemsystemsystem
system
element
system
element
system
system
element
system
element
system
element
system
elementsystemsystem
system-of-interest
     
Hierarchy
(The depth of the
hierarchy depends on
the scope of interest)
Recursion
A system is
comprised of
systems
(and elements)
Dr. Amir Tomer, Kinneret College 4 Software Intensive Systems Modeling

5. Properties of a System
• System – Definition*
– combination of interacting elements organized to achieve one or more
stated purposes
• Thus, each system has the following properties
– Purpose(s)
– Elements
– Interaction (among its elements)
– Organization (over its elements)
• System Element – Definition*
– member of a set of elements that constitutes a system
• Thus, according to the recursive-hierarchical structure, a system element may
be either
– A system by itself – possessing all system properties
– An elementary (atomic) entity – possessing just purpose(s)
*ISO/IEC/IEEE 15288
Dr. Amir Tomer, Kinneret College 5 Software Intensive Systems Modeling

6. “Block” – a unified notion
• In order to obtain unified modeling concepts for systems and elements at all
levels
– i.e. System-of-system, system, subsystem, assembly, component, unit, etc.
we define a unified entity, noted as “Block”, as follows:
1. A system is a block
2. A system is composed of one or more blocks
3. An element (system element) is a block, which is atomic (non-decomposable)
4. Every block has one or more purposes
5. A system has an organization (over its blocks)
6. A system has an interaction (among its blocks)
Based on the “composition” design pattern: Vlissingen et al, Design Patterns, 1994
1
2
3
4
5
6
<<abstract>>
Block
+ Purpose [1...*]
System
- organization
- interaction
Element
1..*
Legend
inheritance relation
composition relation
+ P public property
- P private property
Dr. Amir Tomer, Kinneret College 6 Software Intensive Systems Modeling

7. The Four Views of a Block (System/Element)
Environment
The connection points
(interfaces) between the block
and its external entities
Services (Functions)
The provided/acquired
services(functions) to/from
external entities and the way
these services are obtained
Structure
(non-atomic blocks only )
The elements comprising
the block and their
interrelations
Behavior
The activities the block needs to
perform in order to provide its
services
Static Viewpoint Dynamic Viewpoint
External
Viewpoint
(Black Box)
Internal
Viewpoint
(White Box)
purpose
Interaction
Organization
Dr. Amir Tomer, Kinneret College 7 Software Intensive Systems Modeling

8. A Systematic Systems Engineering Process (SEP)*
* Systems Engineering Fundamentals, DOD, 2001 and IEEE-Std-1220
Dr. Amir Tomer, Kinneret College 8 Software Intensive Systems Modeling

9. Modeling in the Requirements Analysis Phase
Requirements Analysis
– Analyze Missions and Environments
– Identify Functional Requirements
– Define/Refine Performance and Design Constraint
Requirements
Environment Services
Structure Behavior
Static Dynamic
External
Internal
Functional
Requirements
Design Constraints
And non-functional
requirements
Dr. Amir Tomer, Kinneret College 9 Software Intensive Systems Modeling

10. Modeling in the Functional Analysis Phase
Functional Analysis
– Decompose to Lower-Level Functions
– Allocate Performance and Other Limiting Requirements to
All Functional Levels
– Define/Refine Functional Interfaces (Internal/External)
– Define/Refine/Integrate Functional Architecture
Environment Services
Logical
Structure
Physical
Logical
Behavior
Physical
Static Dynamic
External
Internal
Functional
(Logical)
Design
Dr. Amir Tomer, Kinneret College 10 Software Intensive Systems Modeling

11. Modeling in the Design Synthesis Phase
Design Synthesis
– Transform Architectures (Functional to Physical)
– Define Alternative System Concepts, Configuration Items
and System Elements
– Select Preferred Product and Process Solutions
– Define/Refine Physical Interfaces (Internal/External)
Environment Services
Logical
Structure
Physical
Logical
Behavior
Physical
Static Dynamic
External
Internal
Physical Design
(Architecture)
Subject to design constraints
And other non-functional requirements
Dr. Amir Tomer, Kinneret College 11 Software Intensive Systems Modeling

12. From Block to Sub-Block Modeling
• The requirements of a
sub-blocks are directly
derived from the
parent-block’s design
Environment Services
Structure Behavior
A-1
A-3
A-2
A-1 A-3 A-2
f
f
A-1 A-2A-3
Environment Services
Structure Behavior
Block A: Design
Sub-Block A-3: Requirements
Design
constraints
+
non-functional
requirements
Dr. Amir Tomer, Kinneret College 12 Software Intensive Systems Modeling

13. “Business”
The “Five Levels of Interest” of a Software-Intensive System (SWIS)
• The general definition of a “system” allows unlimited depth of hierarchical breakdown
– Although this is applicable also for SWISs, there are 5 types of levels, for which certain
model types are preferred for the sake of modeling effectiveness
Software Intensive System (SWIS)
Hardware Platforms & Devices
(Hardware Configuration Items = HWCIs)
These will be considered as either:
- atomic elements
- SWISs, requiring further breakdown
Software Applications
(Computer SW Configuration Items = CSCIs)
Computer Software Components (CSCs)
Computer Software Units (CSUs)
Humans
Equipment
Users and other Stakeholders
Other SWISs
Dr. Amir Tomer, Kinneret College 13 Software Intensive Systems Modeling

14. Related Topics and Issues
• Choosing the right model for each view
– The use-case/state-machine/activity-diagram dillema
• Model consistency
– Between models on the same breakdown level
– Between breakdown levels
• Model verification
– Correctness, quality, applicability etc.
• Life-cycle architecture modeling
– Test architecture, production architecture, maintenance architecture, …
• Balancing visual and textual specifications
– One picture vs. 1000 words
• Non-top-down engineering modeling (re-engineering, reverse engineering, …)
– Open-source style, unsynchronized system arrays
Dr. Amir Tomer, Kinneret College Software Intensive Systems Modeling14

15. Any questions?
15 Software Intensive Systems ModelingDr. Amir Tomer, Kinneret College
amir@amirtomer.com
052-8890202